406 MOLLUSCA. 



Fam. 1. Actaeonidae. Cephalic disc bifid behind. Shell external with 

 prominent spire, entirely covering animal ; operculum horny ; visceral loop 

 streptoneurous ; epipodia absent. Actaeon Montf. (Fig. 317). 



Fam. 2. Eingiculidae. Cephalic disc forms behind an open tube. Shell 

 external with prominent spire, without operculum. Ringicula Deshayes. 



Fam. 3. Tornatinidae. Shell as before, but spire concealed. Radula absent. 

 Tornatina Adams ; Volvula Adams. 



Fam. 4. Scaphandridae. Shell external, without projecting spire ; cephalic 

 disc short, truncated behind ; radula with first lateral very large ; epipodia well 

 developed ; stomach with three well-developed calcareous plates. Scaphander 

 Montf. ; Cylichna Loven ; Amphisphyra I*) veil ; Atys Montf. ; Smaragdinella Ad. 

 .Fam. 5. Bullidae. Shell external without projecting spire; cephalic disc 

 bifurcated behind ; epipodia large ; radula usually multiserial. Bulla L., 

 bubble-shell; Accra Mliller. 



The Aplustridae (Aplustrum Schumacher) are allied here. 



Fam. 6. Philinidae. Shell internal; epipodia large; cephalic disc simple. 

 Philine Ascanius, three calcareous stomach - plates ; Doridium Meckel, no 

 stomach-plates, two posterior pallial appendages; Gastropteron Meckel, mantle 

 and shell much reduced, epipodia large, united behind. 



Fam. 7. Enncinidae. Cephalic shield and mantle continuous ; shell absent ; 

 four stomach-plates. Runcina Forbes (Pclta Quatrefages). 



The following three families were formerly united as Pteropoda Thecosomata, 

 characterized by their foot extending round the dorsal side of the head and 

 being entirely transformed into two anterior lateral fins, by the existence of a 

 mantle-fold, by the absence, in the adult, of a ctenidium (except in certain 

 Cavolinia] and of eyes, by the presence of one pair of tentacles of which the 

 right is often the larger, by the position of the cerebral ganglia at the sides of 

 the oesophagus, by the radula having three teeth in each row (1:1:1), by the 

 stomach containing horny plates, and by being pelagic in habit. By the 

 operculum of Limacina they are allied to Actaeon, and by the approximation of 

 the pleural to the cerebral ganglia and by the stomach-plates, they are allied to 

 the Bulloidca generally. The heart has one auricle and one ventricle ; the 

 kidney is on the right side, and opens into the pericardium and into the mantle- 

 cavity. The genital glands open on the right side, and there is a ciliated 

 groove for the sperm leading from the opening to the penis, which is anterior 

 and cephalo-dorsal. 



Fam. 8. Limacinidae. Fins large, mantle-cavity dorsal ; shell spiral, 

 sinistral (ultradextral), operculate. Anus, etc., on right side. Peraclis Forbes ; 

 Limacina Cuvier. 



Fam. 9. Cymbuliidae. Adult without shell ; a cartilaginoid pseudo-shell, 

 subepithelial and formed by the connective tissue ; mantle -cavity ventral. 

 Larva with a calcareous, spiral operculate shell. Cymbulia Per. et Les. : Tied- 

 mannia D. Chiaje ; Cymbuliopsis Pelseneer ; Gleba Forskal ; Desmopterus Chun. 



Fam. 10. Cavoliniidae. Visceral mass and shell not coiled, symmetrical ; 

 pallia] -cavity ventral. Cavolinia Abildgaard (Hyalea Lam., Fig. 319) ; Cuvierina 

 Boas ; Clio L., with subgenera Crcseis Rang (Fig. 320), Hyalocylix Fol, and 

 Styliola Les. 



The Lophocercidae are allied to the Bulloidea. They have an external shell, 

 a long foot, epipodia separated from the ventral face of foot, and a short visceral 

 commissure, and a ctenidium and branchial chamber on right side. Lobiger 

 Krohn ; Lophocercus Krohn. 



